1. Field of the Invention
The present invention relates to a cleaning technique of an ink jet recording head.
2. Description of the Related Art
Ink jet recording apparatuses are widely used as apparatuses for recording an image on a recording medium. In forming an image using an ink jet recording apparatus, a heater which is provided in a nozzle in a recording head is heated and a bubble is instantaneously generated by the heat. Then, under the pressure of the bubble, ink is discharged from a discharge port of the nozzle. Generally, ink in the nozzle of the ink jet recording apparatus thickens as time passes and tends to fix to the nozzle. This causes defective discharge such as nozzle clogging and impact deviation. Further, ink cannot be discharged from the nozzle when a bubble is gradually generated in the ink discharge nozzle. This also causes the defective discharge. When the defective discharge occurs, color irregularity or density non-uniformity appears in streaks on the recording image.
When the defective discharge occurs, the mode of the recording apparatus is changed to a head cleaning mode and the head is recovered by cleaning processing. According to the cleaning processing, preliminary discharge operation or forced suction is performed. When the preliminary discharge operation is performed, ink is discharged from the nozzle for the purpose other than image recording. When the suction operation is performed, the clogged ink is forcibly removed and discharged under suction. However, since waste ink is produced according to these operations, the running costs of the recording apparatus are increased.
Further, if a large bubble that involves a plurality of nozzles is generated in the recording head or in the ink flow path, the bubble may not be removed by the above-described preliminary discharge operation or the suction operation. Japanese Patent Application Laid-Open No. 9-11496 discusses a method for removing such a bubble by circulating ink from an ink tank through an ink supply flow path by, for example, a pump. Owing to the ink circulation, the bubble in the ink flow path is drawn in the ink tank and the ink can be discharge normally again.
On the other hand, in some cases, paper dust and airborne undesired substance (hereinafter referred to as a “dust particle”) adheres to the nozzle face. When the dust particle adheres to the nozzle face, the impact accuracy of the ink droplet is decreased and a streak is generated on the image formed under the defective discharge state. It is difficult to remove all the dust particles by the above-described preliminary discharge operation and the suction operation. A known method for removing such a dust particle is using the wiping mechanism. By using an elastic blade, the nozzle face is wiped and the dust particle is removed.
Although the method discussed in Japanese Patent Application Laid-Open No. 9-11946 is effective in recovering the defective discharge due to a bubble by circulating ink, it is not effective in recovering the defective discharge due to an adhering dust particle. On the other hand, although the adhering dust particle can be removed by blade wiping, it is not effective when the defective discharge is caused by a bubble.